Casing for turbine engine having a cooling unit

ABSTRACT

A turbine inner shell for a turbine engine includes one or more mounting grooves, each of which receives a fluid conduit. A temperature controlling fluid is circulated through fluid conduit to selectively heat or cool surrounding portions of the turbine inner shell, to thereby control the thermal growth of those portions of the turbine inner shell. This makes it possible to selectively control a clearance between the tips of rotating turbine blades and the surrounding shrouds of the turbine.

BACKGROUND OF THE INVENTION

Industrial turbine engines include a compressor section, a combustorsection and a turbine section. In the turbine section, multiple rows ofturbine blades (or buckets) mounted on a rotor rotate betweencorresponding rows of stationary nozzles. For each row of turbineblades, a circumferential shroud is mounted on the turbine casing, theshroud being positioned just outside the tips of the turbine blades inthe radial direction.

A clearance must be maintained between the tips of the turbine bladesand shroud to prevent the tips of the turbine blades from rubbing theshroud as the turbine blades rotate. However, it is desirable to keepthe clearance as small as possible to prevent the motive gas fromescaping around the tips of the blades. Generally speaking, the smallerthe clearance, the more efficient the turbine.

During transient periods, such as when the turbine is starting, or whenthe turbine increases or decreases load or rotational speed, variouselements within the turbine section can increase or decrease intemperature. Unfortunately, the various elements do not tend to increaseand decrease in temperature at the same rate. For example, duringstartup operations, the turbine blades tend to increase in temperaturemore rapidly than the turbine casing, which holds the shroud surroundingthe tips of the turbine blades. The turbine blades are mounted on disks,and the disks also heat up and expand outward in the radial direction.

When one portion of the turbine increases in temperature more rapidlythan other portions, the portions that are heated more rapidly canexperience more rapid thermal expansion/growth than the portions thatare increasing in temperature more slowly. During startup operations, ifthe turbine blades increase in temperature more rapidly than the turbinecasing holding the shrouds, the turbine blades can experience more rapidthermal growth in the radial direction than the turbine casing.

Moreover, the different parts of the turbine mare made of differentmaterials which have different coefficients of thermal expansion. Evenif all the elements increased in temperature at the same rate, thedifferences in the coefficients of thermal expansion of the variousmaterials would still cause the various elements to grow differentamounts relative to each other.

Another factor is the loading applied to the various elements. Theturbine blades, and the disks upon which they are mounted, experiencemechanical centripetal forces due to the fact that the blades and disksare rotating. This also can cause the disks and turbine blades to growin the radial direction. At relatively low rotational speeds, there isrelatively little growth due to this mechanical loading. However, as therotational speed increases, the blades and disks tend to grow longer. Incontrast, the shroud surrounding the turbine blades is not rotated anddoes not experience any growth due to centripetal forces.

Designers must take all of these factors into account when specifyingthe dimensions of the elements of the turbine to ensure that at anygiven point in time, the turbine blades do not grow so long in theradial direction that they begin to rub against the shroud. However,when the elements of the turbine are designed to ensure that a clearanceis maintained between the tips of the turbine blades and the shroud atall times, this can result in the clearance being larger than desirableduring steady state operations, which can negatively impact theefficiency of the turbine engine.

To address this issue, selected portions of the turbine casing can beheated and/or cooled during transient periods, or during steady stateoperations, to control the position of the shroud in the radialdirection. This, in turn, controls the clearance between the tips of theturbine blades and shroud. Selective heating or cooling of portions ofthe turbine casing during a transient period can ensure that a clearanceis maintained between the tips of the turbine blades and the shroudduring the transient period. Selective heating and/or cooling of theturbine casing during steady state operations can decrease the clearancebetween the tips of the turbine blades and the shroud to a desiredminimum dimension, to thereby maximize the efficiency of the turbineengine.

Prior art attempts to selectively heat and/or cool the turbine casinghave required that coolant passages be formed in the turbine casing atselected locations, such as just outside the shrouds in the radialdirection. Manufacturing the turbine casing in this fashion can beexpensive and difficult. Also, it is impossible to retrofit such designsinto existing turbine engines. The turbine casing must be manufacturedfrom the start to include the coolant passages.

SUMMARY OF THE INVENTION

In a first aspect, the invention may be embodied in an inner shell forthe turbine section of a turbine engine that includes a plurality ofarcuate casing portions that are configured to be attached to oneanother to form a generally cylindrical inner shell. Each arcuate casingportion includes at least one shroud hook portion that extends along aninterior side of the arcuate casing portion in a circumferentialdirection, and at least one mounting groove that extends along thearcuate casing portion in the circumferential direction. Each at leastone mounting groove is located adjacent to one of the at least oneshroud hook portions. At least one conduit having at least one internalpassageway for a temperature controlling fluid is mounted within one ofthe at least one mounting grooves. The at least one conduit isconfigured to be slid into a mounting groove in the circumferentialdirection.

In another aspect, the invention may be embodied in a temperaturecontrolling fluid conduit that is configured to be mounted on anarcuate-shaped portion of an inner shell of a turbine section of aturbine engine. The fluid conduit includes an elongated, arcuate-shapedbody having an interior passageway for a temperature controlling fluid,and at least one inlet aperture that is configured to admit a flow of atemperature controlling fluid into the interior passageway

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the interface between rotating turbineblades in the turbine section of a turbine engine and surroundingportions of the turbine shell;

FIG. 2 is a diagram illustrating a fluid conduit that is partially slidinto a mounting groove of a turbine inner shell;

FIG. 3 is a diagram illustrating a fluid conduit fully installed in amounting groove of a turbine inner shell;

FIG. 4 is a cross-sectional view of a first embodiment of a fluidconduit installed in a mounting groove of a turbine inner shell;

FIG. 5 is a cross-sectional view of a second embodiment of a fluidconduit installed in a mounting groove of a turbine inner shell;

FIG. 6 is a partial perspective view of a portion of a first embodimentof a temperature controlling fluid conduit having protrusions onexterior surfaces;

FIG. 7 is a partial perspective view of a portion of a second embodimentof a temperature controlling fluid conduit having protrusions onexterior surfaces; and

FIG. 8 is a cross sectional view of a third embodiment of a fluidconduit installed in a mounting groove of a turbine inner shell.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a diagram illustrating a portion of a turbine section of aturbine engine. FIG. 1 shows the turbine outer shell 100 and the turbineinner shell 110. The tips of two rows of turbine blades 122 and 124 areshown. The rows of turbine blades 122, 124 are mounted on a rotor of theturbine and the turbine blades rotate relative of the inner surface ofthe turbine inner shell 110. A row of stationary nozzles 130 is mountedon the turbine inner shell 110 between the two rows of turbine blades122, 124.

Circumferentially extending shrouds 142, 144 are mounted on the turbineinner shell 110 at positions opposite the tips of the rotating turbineblades 122, 124. The shrouds 142, 144 are mounted on shroud hooks in theturbine inner shell 110. As explained in the Background section above,it is necessary to maintain a clearance between the tips of the rotatingturbine blades 122, 124 and the stationary shrouds 142, 144. However, itis also desirable to minimize the clearance to maximize the efficiencyof the turbine engine.

FIG. 1 illustrates that temperature controlling fluid passageways 150,152 are formed in the turbine inner shell 110. Heated fluid can becirculated in the temperature controlling fluid passageways 150, 152 toraise the temperature of the turbine inner shell, which will cause theinner shell 110 to expand outward radially, increasing the clearancebetween the shrouds 142, 144 and the tips of the turbine blades 122,124. At the same time, increasing the temperature of the shrouds tendsto cause thermal growth of the shrouds, which tends to decrease theclearance. These factors must be balanced to ensure that a propertemperature fluid is used to cause the clearance to be adjusted in theproper way.

Conversely, a cooling fluid can be circulated through the temperaturecontrolling fluid passageways 150, 152 to lower the temperature of theturbine inner shell 110, which will cause the turbine inner shell 110 tocontract inward radially, decreasing the clearance between the shrouds142, 144 and the tips of the turbine blades 122, 124. At the same time,cooling the shrouds causes the shrouds to contract, which tends toincrease the clearance. Here again, the temperature of the fluid must becarefully controlled to ensure the proper clearance is maintained.

At different times it may be advantageous to increase or decrease theclearance using an appropriate temperature fluid. However, a design asillustrated in FIG. 1 requires that fluid passageways be formed in theturbine inner shell, which can be expensive.

FIG. 2 illustrates a design embodying the invention for a turbine innershell 110 of a turbine engine that includes a fluid conduit 200 that cancarry a flow of temperature controlling fluid. The turbine inner shellof a turbine engine is typically comprised of two or more arcuate-shapedsections that are bolted together to form a generally cylindricalturbine inner shell. FIG. 2 illustrates a portion of one arcuate-shapedsection of the turbine inner shell 110. FIG. 2 also illustrates thatseveral shroud hooks 114 are formed on the radially inner surface of theturbine inner shell 110. Shrouds that would confront the tips ofrotating turbine blades are mounted on the shroud hooks 114.

A mounting groove 120 is formed in the turbine inner shell 110 at alocation that is radially outside and immediately adjacent to one of thesets of shroud mounting hooks 114. An elongated, arcuate-shaped conduit200 is mounted in the mounting groove 120. FIG. 2 shows the fluidconduit 200 partially inserted into the mounting groove 120. FIG. 3illustrates the fluid conduit 200 fully inserted into the mountinggroove 120. FIGS. 2 and 3 also illustrate that a mounting block portion240 on the fluid conduit is aligned with a mounting block portion 112 ofthe turbine inner shell 110 when the fluid conduit 200 is fully insertedinto the turbine inner shell 110.

FIG. 4 illustrates a cross-sectional view of a first embodiment of afluid conduit 200 mounted in a mounting groove 120 of a turbine innershell 110. The fluid conduit 200 has a lower surface portion 210 thatabuts a wall 116 separating the mounting groove 120 from the locationwhere a shroud is mounted on shroud mounting hooks 114.

The fluid conduit 200 has a stepped shape that includes an upper portion230 having a smaller cross-sectional area which encloses a firstinterior passageway 232 and a lower portion having a largercross-section that encloses a second interior passageway 220. Aseparation wall 222 with a plurality of apertures 234 separates thefirst interior passageway 232 from the second interior passageway 220.

The upper portion 230 also provides stiffness and rigidity to thestructure, which helps the lower portion to retain its shape. This, inturn, helps to prevent any deformation of the lower portion fromaffecting the shape and position of the underlying shroud.

A supply pipe 250 is attached to the upper, portion 230 of the fluidconduit 200. The supply pipe 250 delivers a flow of temperaturecontrolling fluid into the first interior passageway 232. Thetemperature controlling fluid can flow in a circumferential directionalong the first interior passageway 232. The temperature controllingfluid can also pass through the apertures 234 in the separation wall 222to enter the second interior passageway 220. The separation wall 222with apertures 234 helps to cause a flow of temperature controllingfluid that is delivered into the first interior passageway 232 to beevenly distributed circumferentially around the turbine inner shell 110before the temperature controlling fluid enters the second interiorpassageway 220 via the apertures 234.

The flow of temperature controlling fluid that enters the secondinterior passageway 220 escapes from the fluid conduit 200 via aplurality of apertures 212 that pass through the lower wall 210 of thefluid conduit 200. As will be explained in greater detail below, theexterior walls of the fluid conduit 200 are spaced from the interiorwalls of the mounting groove 120. As a result, the temperaturecontrolling fluid can pass along the gap between the exterior walls ofthe fluid conduit 200 and the interior walls of the mounting groove 120,and ultimately escape to a location radially outside the turbine innershell 110. The arrows in FIG. 4 illustrate the flow of the temperaturecontrolling fluid as it passes from the supply pipe 250 into the firstinterior passageway 232, from the first interior passageway 232 to thesecond interior passageway 220, out the apertures 212, around theexterior sides of the fluid conduit 200 and out to the location radiallyoutside the turbine inner shell 110.

In alternate embodiments, the fluid that is circulated through the firstand second interior passageways need not be routed to a locationradially outside the inner shell 110. Instead, the fluid could becollected and used for other purposes inside the turbine inner shell110.

The configuration illustrated in FIG. 4 results in the temperaturecontrolling fluid impinging on the wall 116 that is adjacent the shroudmounting hooks 114. As a result, the temperature controlling fluid canheat or cool the portions of the turbine inner shell and the shroudsthat are directly opposite the tips of the rotating turbine blades. Thisprovides rapid and effective control over the thermal growth of theseportions of the turbine, and thus the clearance between the turbineblades and the shroud.

The stepped shape of the mounting groove 120 and the correspondingstepped shape of the fluid conduit 200 allow the fluid conduit 200 to beeasily mounted on the turbine inner shell 110. The stepped shape, wherethe radially outer portion has a smaller cross-sectional shape than theradially inner portion, ensures that the fluid conduit is trapped on theturbine inner shell 110 without the use of mounting hardware. Othershapes for the mounting groove 120 and fluid conduit 200 could achievesimilar functions. For example, the mounting groove 120 and fluidconduit 200 could have a trapezoidal or triangular shape, where theradially outer portions have a smaller dimension than the radially innerportions. Also, in some embodiments, the shape of the mounting grooveneed not match the shape of the fluid conduit.

FIG. 5 illustrates an alternate configuration for the fluid conduit 200.In this embodiment, no separation wall is provided between the firstfluid passageway 232 and the second fluid passageway 220. Thisembodiment may be advantageous in embodiments where ensuring that thetemperature controlling fluid is circumferentially distributed is not asimportant. The lack of the separation wall would decrease the flowrestrictions.

FIG. 6 illustrates that a plurality of protrusions 242, 244, 246 couldbe formed on exterior walls of a fluid conduit 200 embodying theinvention. The protrusions 242, 244, 246 serve to space the exteriorwalls of the fluid conduit 200 from the interior walls of a mountinggroove 120 in the turbine inner shell 110. Maintaining a spacing allowsthe temperature controlling fluid to pass along the space between theexterior walls of the fluid conduit 200 and the interior walls of themounting groove 120, as illustrated in FIGS. 4 and 5. Although not shownin FIG. 6, similar protrusions would be formed on the bottom wall of thefluid conduit 200.

In the embodiment illustrated in FIG. 6, the protrusions 242, 244, 246are elongated in the length direction of the fluid conduit 200. Also,the leading and trailing edges of the protrusions are tapered. Thetapered, elongated shape of the protrusions 242, 244, 246 is designed tofacilitate sliding of the fluid conduit 200 into a mounting groove 120of the turbine inner shell 110.

FIG. 7 illustrates an alternate embodiment of a fluid conduit 200. Inthis embodiment, the protrusions are formed as ridges 248 that extendaround the exterior walls of the fluid conduit 200. Although only asingle ridge 248 is illustrated in FIG. 7, multiple ridges 248 would belocated along the length of the fluid conduit 200. The ridges 248 extendin essentially the same direction that the temperature controlling fluidflows along the exterior sides of the fluid conduit 200. Thus, theridges 248 would not impede the flow, and may serve to guide the flow ofthe temperature controlling fluid.

FIG. 8 illustrates another embodiment of a fluid conduit 300 mounted ina mounting groove 320 of a turbine inner shell 110. In this embodiment,no protrusions are formed on the exterior walls of the fluid conduit300. As a result, the bottom wall 310 and the side exterior walls of thefluid conduit 300 may be in direct contact with the inner walls of themounting groove 320.

When an embodiment of a fluid conduit as illustrated in FIG. 8 is usedin a turbine inner shell 110, one or more of the pipes coupled to theinterior passageway 320 of the fluid conduit 300 would be used todeliver an incoming flow of temperature controlled fluid into theinterior passageway 320, and one or more of the pipes coupled to theinterior passageway 320 would remove a flow of the temperaturecontrolling fluid. The pipes used to deliver an incoming flow and thepipes used to withdraw an outgoing flow would be positioned around thefluid conduit to cause a predetermined flow pattern through the interiorpassageway 320 of the fluid conduit 300.

A fluid conduit as described above can be easily mounted to a turbineinner shell to help control a clearance between the tips of the turbineblades and the surrounding shrouds. The fluid conduits can be easilyinserted into and removed from the corresponding mounting grooves whenthe sections of the turbine inner shell are separated for maintenanceand repair. Also, mounting grooves for the fluid conduits describedabove can be machined into existing turbine inner shells, making itpossible to retrofit such fluid conduits into existing turbines whichlack any way to actively control the clearance between the tips of theturbine blades and the surrounding shrouds.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. An inner shell for the turbine section of a turbine engine, comprising: a plurality of arcuate casing portions that are configured to be attached to one another to form a generally cylindrical inner shell, wherein each arcuate casing portion includes: at least one shroud hook portion that extends along an interior side of the arcuate casing portion in a circumferential direction, and at least one mounting groove that extends along the arcuate casing portion in the circumferential direction, wherein each at least one mounting groove is located adjacent to one of the at least one shroud hook portions; and at least one conduit having at least one internal passageway for a temperature controlling fluid, each conduit being mounted within one of the at least one mounting grooves, wherein the at least one conduit is configured to be inserted into a mounting groove.
 2. The inner shell of claim 1, wherein a radial inner side of the at least one mounting groove has a larger width than a radial outer side of the at least one mounting groove.
 3. The inner shell of claim 1, wherein each at least one mounting groove is located on a radially outer side of one of the at least one shroud hook portions.
 4. The inner shell of claim 1, wherein the internal passageway of each at least one conduit extends in a length direction of the conduit.
 5. The inner shell of claim 4, wherein each at least one conduit includes a plurality of apertures that extend from the interior passageway to an exterior of the conduit.
 6. The inner shell of claim 5, wherein the plurality of apertures are formed on a side of the conduit that faces the at least one shroud hook portion.
 7. The inner shell of claim 5, wherein each at least one conduit includes a plurality of protrusions that are formed on an exterior surface of the conduit.
 8. The inner shell of claim 7, wherein the plurality of protrusions are configured to space exterior surfaces of the conduit from interior surfaces of the at least one mounting groove.
 9. The inner shell of claim 1, wherein each at least one conduit includes: a first interior passageway that extends in a length direction of the conduit; a second interior passageway that extends in a length direction of the conduit, wherein the first interior passageway is located on a radial outer side of the second interior passageway; and a plurality of radially extending apertures that extend between the first and second interior passageways.
 10. The inner shell of claim 1, wherein each at least one conduit further includes at least one inlet aperture that is configured to admit a flow of a temperature controlling fluid into the interior passageway.
 11. The inner shell of claim 1, wherein the at least one conduit is configured to be slid into a mounting groove in a circumferential direction.
 12. A temperature controlling fluid conduit that is configured to be mounted on an arcuate-shaped portion of an inner shell of a turbine section of a turbine engine, comprising: an elongated, arcuate-shaped body having an interior passageway for a temperature controlling fluid; and at least one inlet aperture that is configured to admit a flow of a temperature controlling fluid into the interior passageway.
 13. The temperature controlling fluid conduit of claim 12, wherein a radial inner side of the elongated body has a larger width than a radial outer side of the elongated body.
 14. The temperature controlling fluid conduit of claim 12, wherein the at least one inlet aperture is located on a radial outer side of the elongated, arcuate-shaped body.
 15. The temperature controlling fluid conduit of claim 12, wherein the interior passageway extends in a length direction of the elongated arcuate-shaped body.
 16. The temperature controlling fluid conduit of claim 15, wherein a plurality of apertures extend through the elongated, arcuate-shaped body from the interior passageway to an exterior of the body.
 17. The temperature controlling fluid conduit of claim 16, wherein the plurality of apertures are formed on a radial inner side of the elongated, arcuate-shaped body.
 18. The temperature controlling fluid conduit of claim 16, wherein a plurality of protrusions are formed on at least one exterior surface of the elongated, arcuate-shaped body.
 19. The temperature controlling fluid conduit of claim 12, wherein the interior passageway comprises: a first interior passageway that extends in a length direction of the elongated, arcuate-shaped body; a second interior passageway that extends in the length direction of the elongated, arcuate-shaped body, wherein the first interior passageway is located on a radial outer side of the second interior passageway; and a plurality of radially extending apertures that extend between the first and second interior passageways. 